Peptide potentiation of acid-sensory ion channel in pain

Abstract

An assay for determining agonists, antagonists, or modulators for acid-sensing ion channels. The assay is especially useful for screening analgesics. The screening assay can be provided in a kit form. The assay comprises administering the composition to be screened to cells expressing acid-gated channels and then determining whether the composition inhibits, enhances, or has no effect on the channels when acid is introduced. The determination can be performed by analyzing whether a current is sustained by the cells in the presence of the composition and the acid. This current can be compared to that sustained by the FMRFamide and related peptides.

What is claimed is:  
     
       1. A method for screening compositions to identify agonists, antagonists, or modulators of acid-sensing ion channels comprising 
       administering the composition to be screened to cells expressing acid-gated channels in the presence of acid and FMRFamide or FMRFamide-related peptides, and determining whether the composition enhances or inhibits the opening of the acid-sensing ion channels of the DEG/ENaC channel family.  
     
     
       2. The method of  claim 1  wherein the determination of opening of the acid-sensing ion channels is via electrophysical analysis. 
     
     
       3. The method of  claim 2  wherein the electrophysical analysis looks for a sustained current in the channels. 
     
     
       4. The method of  claim 2  wherein the electrophysical analysis looks for inactivation of a current in the channels. 
     
     
       5. The method of  claim 1  wherein the determination of opening of the acid-sensing ion channels is via a method selected from the group consisting of voltage-sensitive dyes, ion-sensitive dyes, and cell death assays. 
     
     
       6. The method of  claim 1  wherein the acid-gated channels are selected from the group consisting of ASIC and DRASIC channels. 
     
     
       7. The method of  claim 1  wherein the cells are selected from the group consisting of DRG neurons, Xenopus oocytes, HEK-293T cells, cultured cell lines, and central nervous system cells. 
     
     
       8. A method for screening compositions to identify analgesics comprising 
       administering the composition to be screened to cells expressing acid-gated channels, and  
       determining whether the composition inhibits the opening of the acid-sensing ion channels of the DEG/ENaC channel family in the presence of acid and FMRFamide or related peptides.  
     
     
       9. The method of  claim 8  wherein the determination is via electrophysical analysis. 
     
     
       10. The method of  claim 9  wherein the electrophysical analysis looks for inhibition or inactivation of sustained current in the channels. 
     
     
       11. The method of  claim 8  wherein the determination of opening of the acid-sensing ion channels is via a method selected from the group consisting of voltage-sensitive dyes, ion-sensitive dyes, and cell death assays.